The invention relates to a rudder unit or vertical tail fin for aircraft. The present invention relates, in particular, to the connection for a rudder unit on the fuselage of an aircraft.
The outside contour of an aircraft results from the interrelationship between aerodynamic and mechanical or static requirements or ideal conceptions. In the ideal case, the contour of all external components is adapted to the ideal aerodynamic conditions. This results in the design options for the supporting structure, as well as the arrangement of the individual equipment components of the aircraft, being limited by the outside contour of the aircraft. In commercial aircraft, in which the rudder unit is directly connected to the tail, the tail section is subjected to higher-than-average mechanical loads, but still needs to fulfill particularly exacting aerodynamic requirements because the elevator and rudder units of the aircraft are accommodated at this location. On one hand, a certain outside contour of the rudder unit and the tail is required in order to realize a rudder unit that conforms to the aerodynamic requirements. On the other hand, all components required for the transmission of the corresponding forces and for ensuring the respective system functions of the elevator and rudder units need to be accommodated within an extremely confined space. Consequently, known solutions of aircraft tail sections and, in particular, the connection for the rudder unit on the tail section of the fuselage always constituted advantageous compromises between the requirements with respect to the laws of aerodynamics and the feasibility with respect to mechanical considerations.
Known connections for a rudder unit on the fuselage of an aircraft consist, for example, of multiple-bolt connections as they have been used so far on all Airbus aircraft. DE 44 04 810 C2 describes an aft fuselage of a commercial aircraft, in which the rudder unit is connected to the fuselage with the aid of the above-mentioned multiple-bolt connections. The rudder unit forces concentrated in the fittings described in this publication are introduced into the corresponding counter fittings on the corresponding fuselage frames and then distributed into the fuselage tail structure as planar as possible. In aircraft such as, for example, Airbus aircraft, three fittings arranged on the left side and three fittings arranged on the right side are bolted to the counter fittings on the fuselage side outside the streamline contour in order to create the widest base possible for the connection. The air current disturbed by these bolt connections is provided with an enveloping aerodynamic fairing [sic] that, however, results in an undesirable increase in the aerodynamic drag.
The multiple-bolt connections used so far for connecting the rudder units require a concentration of the flows of forces that is distributed over the spar cross sections in a planar fashion into a more or less line-shaped bolt structure that, in addition, is offset relative to the centroidal axis. The counter fittings of the bolt structure on the fuselage side then need to introduce this concentrated flow of forces into the fuselage tail structure as planar as possible.
The concentration of the forces from a large cross section, e.g., of the spars, to a smaller cross section, e.g., of the bolts or fittings, and the repeated reversal of the flow of forces on the fuselage side, as well as the additional moment resulting from the offset of the flow of forces relative to the centroidal axis between the spars that lie within the rudder unit contour and the bolts or fittings that lie outside this contour, may result in additional weight.
This construction results in relatively heavy bolts, fittings and connection structures. The aerodynamic fairing for these connection structures is situated in the region of the rudder unit base that is particularly critical with respect to fluidic considerations and results in additional weight and increased aerodynamic drag.